A dual-targeting mRNA lipid nanoparticle restores ABCA1-dependent cholesterol homeostasis to promote repair of age-related bone defects

Cholesterol regulates autophagy and aging, yet its role in bone marrow mesenchymal stem cell (BMSC) senescence remains unclear. We demonstrate that ABCA1 palmitoylation is associated with its lysosomal localization and lysosome-associated cholesterol transport, thereby contributing to autophagy inhibition, senescence, and impaired osteogenesis. However, directly perturbing ABCA1 palmitoylation impaired cholesterol efflux through plasma membrane-localized ABCA1, increased cellular cholesterol accumulation, and inhibited osteogenesis. To selectively depalmitoylate lysosomal ABCA1, we engineered a lysosome-targeted depalmitoylase, RAB7-APT2 (RA), by fusing RAB7 to APT2, the primary depalmitoylase of ABCA1. Aging-cell-targeted low-inflammatory liposomes were synthesized to deliver RA mRNA, yielding dual-targeted lipid nanoparticle (LNP@A). LNP@A selectively modulated lysosomal ABCA1 localization, reduced lysosomal cholesterol accumulation, restored autophagy, and alleviated senescence in aged BMSCs. Consequently, LNP@A enhanced osteogenesis in vitro and improved bone regeneration in an aged rat defect model. These findings reveal a role for ABCA1 spatial regulation in BMSC aging and provide a targeted strategy for age-related bone regeneration.